There have been typically known various bags attached with a zipper tape that are used for packaging medicine, food and the like (see, for instance, Patent Literature 1).
Such a zipper-tape bag disclosed in patent Literature 1 includes a film forming a bag body and a zipper tape with a surface that is to be bonded to the film, the surface being provided with a predetermined resin layer so that the film and the zipper tape are easily bonded to each other.
A layered film including a seal layer made of a polypropylene resin containing polypropylene at 75 mass % or more with respect to the other resin component has been widely used for food packages.
A zipper tape may be bonded to such a layered film with the seal layer to make a zipper-tape bag. In such a case, a surface of the zipper tape to be bonded to the layered film may be provided with a layer made of a resin well-compatible with the seal layer of the layered film in order to improve a sealing performance at a bonding interface between the zipper tape and the layered film.
The polypropylene resin forming the seal layer of the layered film, however, has a higher melting point than a polyethylene resin. Thus, in sealing a peripheral portion of a bag body to make a bag, a certain amount of heat is necessary for crushing (i.e., point-sealing) parts of male member and female member of the zipper tape at a position located in the peripheral portion of the bag body along with the layered film.
Further, when crushed to make the bag, the resin forming the male member and the female member of the zipper tape spreads in the peripheral portion of the bag body. Accordingly, in order to ensure a sealing performance of the spreading resin in the peripheral portion of the bag body, a layer of the zipper tape that is not bonded to the layered film (i.e., a layer continuous with the male member and the female member) is also made of the same type of resin as that of the seal layer of the layered film.